TSN BasicBot Part Four: Assembly and Tuning

The art of origami is often practiced at the elementary level, where kids learn to create and fold patterned paper into 3-dimensional objects. Origami is a great way to introduce translation and transformation of two-dimensional shapes as they are mirrored across a centerline. In fact it helps to create a foundation for these students later in life as they look at designing for manufacture in our STEM classes. Being comfortable manipulating the geometry of complex shapes in 3-D space is a high level skill that spills into a variety of student STE(A)M coursework.

There are three basic iterations of design in terms of dimension. 3-D objects can be printed directly or cut out on the mill or lathe. Two dimensional objects can be cut on a laser, CNC plasma cutter, or they can be milled as well (technically this can be considered 2.5-D since there is some accounting for height). Finally, 2-D shapes can be designed to be assembled into 3-D objects. This is commonly seen when acrylic or wood is assembled from flat pieces cut on a laser cutter, or metal cut on a CNC plasma is welded into a 3-D part.

As we teach STEM students about the concept of design for manufacture, we ask them to consider time as a cost factor. The time it takes to assemble a 3D object from a set of 2-D parts can be significant. The assembly process can also introduce errors into the final product. We analyze the number of T-slots in an acrylic project box, or count the number of holes that need to be tapped, all with the notion of reducing sources of various costs.

Recent research in Germany has provided an ingenious solution to some of these cost factors for those using acrylic to manufacture parts on a laser. Rather than cutting the parts, laying them out and assembling them, some of the joints are actually bent by applying selective laser heat and drawn down by gravity. What this means is that the creation of 3-D parts is possible using 2-D materials, reducing costs dramatically. It is an extreme example of rethinking the design for manufacture process itself, and should be a great inspiration to students. Extending this inspiration into the classroom as part of student engineering practice is highly recommended, and here is the connection to make it happen. The challenge is to make the process of 2-D laser cutting into a selective bending process that works for your machine. This will engage the students in genuine science and engineering because the process has not been adapted to standard inexpensive laser machines. Watching the video (and reading the research paper) will provide some insight as to what needs to be done. The key is to reduce the intensity of the laser beam and broaden its path in specific locations that will permit bending in the desired area. One possibility is to apply a material or color band on the material that will diffuse the laser and reduce its power. Another is to program the laser to adjust speed and/or power level in different areas along the tool path. The other important factor is the platform and its height must be configured to allow movement of the piece toward the ground. Pay particular attention to the use of a servo motor to rotate the material shown in the video.

This is a project for a team of advanced students. They will need to be familiar with the properties of acrylic as well as the machine and its software. Remember that lasers are dangerous if used carelessly, and the protective cover should always be used. In some cases eye protection should be worn. Whether or not your students perfect this process, they will be engaged in genuine research. If they are successful, they should take every opportunity to share their findings at science fairs, social media and maker web sites. Students who are given the opportunity innovate and experiment in this way are modeling STEM education the way it should be whenever possible. Try it or something similar in your classroom.